Electron beam devices, more particularly a scanning electron microscope (SEM) or a transmission electron microscope (TEM) are used for examining objects in order to obtain knowledge regarding the properties and behavior of said objects under specific conditions.
Both in the case of an SEM and in the case of a TEM, electrons are generated using a beam generator. The electrons emerge from the beam generator and form an electron beam. They are accelerated to a potential on account of a potential difference between the beam generator and an anode. For this purpose, the beam generator is usually supplied with a negative high voltage. In the case of an SEM, said voltage is, for example, in the range of (−1) kV to (−30) kV relative to the ground potential. In the case of a TEM, the high voltage is, for example, in the range of (−10) kV to (−300) kV relative to the ground potential.
In order to achieve examination of an object with a high resolution in the case of the particle beam devices mentioned above, it is desirable for the high voltage made available by a high-voltage supply unit not to be subject to large fluctuations. In order to initiate corresponding measures for stabilizing the high voltage, it is known to measure fluctuations of the high voltage. By way of example, a measuring device having a resistive voltage divider or a capacitive voltage divider is used. The capacitive voltage divider comprises a first capacitor in the form of a high-voltage capacitor and a second capacitor in the form of a measuring capacitor. The first capacitor is accommodated in a housing and sheathed with a high-voltage shield. The housing and the high-voltage shield have a high weight, however, such that the measuring device provided with the capacitive voltage divider is very heavy. By way of example, the weight of a known measuring device designed for 200 kV is several hundred kilograms. Such a high weight makes the handling and the installation of the known measuring device very complicated. In particular, transporting the measuring device to a particle beam device is laborious. Subsequent installation of the known measuring device is therefore possible only with relatively high outlay.
Furthermore, the high-voltage capacitor used in the known measuring device is expensive to procure.
Accordingly, it would be desirable to provide a high-voltage supply unit comprising a measuring device for measuring fluctuations of a high voltage which is cost-effective and simple to handle.